Collapsible energy absorbing vehicular steering columns for application on vehicle steering systems have been well known and in popular use for a number of years.
One such system includes a unitary steering column member of collapsible construction which extends from steering wheel to dash panel and rotatably supports upper and lower telescopically engaged steering shaft sections. Such a system is shown in U.S. Pat. Nos. 3,760,650, 3,805,636, 3,813,960 and 3,815,437.
Another type system includes a two piece steering column assembly having a lower steering column telescopically received within an upper steering column, each rotatably supporting therewithin respective telescopically engaged upper and lower steering shafts. The upper column is commonly supported at the substructure supporting the instrument panel or dash panel. The lower column generally extends to very near the dash panel or may be attached thereto. The lower steering shaft extends through the dash panel and is secured to the gear box. The energy of an impact at the steering wheel by the occupant is generally taken up by some sort of energy absorbing device which is attached to or part of the upper steering column such as shown in U.S. Pat. Nos. 3,855,876 and 4,273,005, or by the energy absorbing device being operatively associated with each of the upper and lower steering column sections such as shown in U.S. Pat. Nos. 3,665,777 and 3,699,824.
In each case, the system is designed to absorb energy over a prescribed predetermined stroke of the one steering column or steering shaft section relative to the other. This predetermined stroke has been designed on the basis of a forward collapse of the steering column, i.e. in the direction of the occupant moving forward and impacting the steering wheel.
With the development of the newer generation of automobiles has come design criteria affecting the vehicle steering system. Among these is included the shorter front end of the vehicles typical with the most recently aerodynamically designed automobiles. Further, the fact that the engine compartment is filled by the engine and transaxle assemblies and other related engine componetry, there is far less free space in the engine compartment. Thus, during a front end collision particularly, there is an increased possibility that the dash panel will intrude into the passenger compartment to a greater extent than otherwise existed.
Should this occur, the overall design mechanics of the system may be adversely affected in that, when the dash panel intrudes, it will force the lower portion of the lower steering column rearward, taking up the available stroke for absorbing any forward travel of the upper steering column as caused by occupant impact with the steering wheel. In U.S. Pat. Nos. 3,724,286, 3,817,118 and 3,832,911, assigned to the assignee of the present invention, is shown a system wherein the forward end of the steering column is offset from the dash panel and the steering shaft is a cable designed to flex in the event of a front end collision and resultant dash intrusion. However, the steering column itself is displaced forwardly by the impact thus reducing the effectiveness of the design.
Further, the prior art steering column assemblies have not addressed the overall design requirements currently placed on steering assemblies as a total system. For example, in addition to the energy absorbing criteria, the system must be lightweight, free from noise and vibration, both as a source, and as a transmitter of noise and vibration from other parts of the vehicle to the hands of the driver. The design must be sufficiently universal to fit numerous vehicular applications, able to accommodate a tilt wheel feature, simple and straightforward in design concept, and relatively inexpensive.
The present invention addresses the foregoing concerns.